Converging weather caused anomalous winter last year

The extraordinarily cold, snowy weather last year, that hit parts of the US East Coast and Europe, was the result of a collision of two periodic weather patterns in the Atlantic and Pacific Oceans, according to new research.

The new study appears in the journal Geophysical Research Letters.

After analysing 60 years of snowfall measurements, a team of scientists at Columbia University’s Lamont-Doherty Earth Observatory found that the anomalous winter was caused by two colliding weather events. El Niño, the cyclic warming of the tropical Pacific, brought wet weather to the southeastern US at the same time that a strong negative phase in a pressure cycle called the North Atlantic Oscillation pushed frigid air from the arctic down the East Coast and across northwest Europe. End result: more snow.

Using a different dataset, climate scientists at the National Oceanic and Atmospheric Administration came to a similar conclusion in a report released in March.

“Snowy winters will happen regardless of climate change. A negative North Atlantic Oscillation this particular winter made the air colder over the eastern U.S., causing more precipitation to fall as snow. El Niño brought even more precipitation-which also fell as snow,” said Richard Seager, a climate scientist at Lamont-Doherty and lead author of the study.

David Robinson, a climate scientist at Rutgers University who was not involved in the research, said: “When the public experiences abnormal weather, they want to know what’s causing it. This paper explains what happened, and why global warming was not really involved. It helps build credibility in climate science.”

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